Sharp ridges crisscross Creede Caldera, and a robust forest of conifer trees lend the feature a deep green hue. Creede Caldera is a well-preserved example of a After a volcano erupts, a caldera forms -- a crater with an elevation lower than its surroundings. When magma moves below this caldera and pushes it upward, the feature becomes a resurgent dome. Geologists were able to discern Creede's structure through extensive mapping and drilling.
Northeast of Creede, lies Wheeler Geologic Monument (also known as the Wheeler Geologic Area), a small, jagged patch of white in this image. The site appears www.sangres.com/features/wheelergeologic.htm more dramatic from the ground. This site is an area of weathering volcanic -- consolidated volcanic ash. Besides weathering, Wheeler Geologic Area's tuff also shows varying degrees of When volcanic ash comes to rest, it is often still hot and pliable. Newer layers of ash land on older layers and compress air bubbles out of the material at the bottom of the heap, turning the lower ash layers into dense, dark rock with a glassy surface. The tuff at Wheeler Geologic Area results from the eruption that formed the pubs.usgs.gov/imap/i2799/ San Luis caldera complex in southwestern Colorado.
NASA image created by Jesse Allen, using data provided courtesy of NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan asterweb.jpl.nasa.gov/ ASTER Science Team.